I agree with the other 2 contributors so far that SEOMoz Whiteboard Friday and Google's own starter guide to SEO are excellent SEO resources.
However, if you're only trying to attract people to your restaurant from the Swansea area then you only need to optimise your site for local searches.
Typically, all you need to do in local SEO is:
- In your website copy, make sure you mention the local towns in your area where you think your customers are likely to come from.
- Sign up for Google Places (this help you to show up better in local searches).
- Get your website listed in a wide variety of online business directories.
That's all you'll probably need to do, as the competition in a relatively small geographical area will be quite low.
To sign up for Google Places go to http://www.google.com/places.